Analysis of maximum pressure in VVER1000/V446 reactor containment for LOCA and MSLB

The highest thermal-hydraulic pressure in the containment occurs when reactor coolant in the first loop and steam in the secondary loop discharge simultaneously,and when the maximum amount of energy from reactor unit enters to containment volume. In this paper, we investigate temperature and pressure variations in the VVER 1000 containment compartments owing to concurrent break in the pipelines of the primary and secondary loops. A two-phase, multicellular model is applied in the presence of non-condensable gases. Convection and conduction through the main heat structures inside the containment are also considered. The predicted results agree well with available data. Maximum values of pressure and temperature in the containment are then calculated and compared to the design values. If LOCA and MSLB occur simultaneously, the maximum pressure would exceed the design value and integrity of the containment would be threatened. (authors)